Upstream: https://github.com/rust-lang/rust/issues/51117

The given example code should not be accepted, as "baz" borrows from "bar" -- the latter should be inaccessible until the former goes out of scope.  Since this isn't properly enforced, a use-after-free becomes possible in safe code.

    fn main() {
        let mut foo = Some("foo".to_string());
        let bar = &mut foo;
        match bar {
            Some(baz) => {
                bar.take();
                println!("{:?}", baz); // UAF, segfaults or prints garbage
            },
            None => unreachable!(),
        }
    }

More analysis upstream, and fixed in https://github.com/rust-lang/rust/pull/51235

There will likely be a 1.26.2 release just to address this, so if possible I'd like to simply update to that:  https://github.com/rust-lang/rust/pull/51258